Hello Kripa,
Thank you for reaching out to Microsoft Support!
After testing, the chat ID extracted manually in the Teams Chat UI is valid, for your error, first you need to check that the account teams is logged in to is the same as the account Graph Explorer is logged in to.
If you have no problems logging into your account, use the List chats endpoint to list all chats in your account and check if the chat ID you manually extracted exists.
Finally, it should be noted that, to access a chat, at least one chat member must belong to the tenant the request initiated from.
Hope this helps.
If the answer is helpful, please click Accept Answer and kindly upvote it. If you have any further questions about this answer, please click Comment.